JP2552365B2 - Active matrix display - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an active matrix display device in which pixel electrodes are arranged in a matrix and high density display is performed.

(Prior Art) Conventionally, in a liquid crystal display device, an EL display device, a plasma display device and the like, a display pattern is formed on a screen by selecting picture element electrodes arranged in a matrix. As a driving method of the picture element electrodes, an active matrix driving method is known in which individual picture element electrodes are arranged and a switching element is connected to each of the picture element electrodes for driving. A TFT (thin film transistor) element, an MIM (metal-insulating layer-metal) element, or the like is generally used as a switching element for selectively driving the pixel electrodes. The active matrix drive system is capable of high-contrast display, and can be used for LCD televisions, word processors,
It has been put to practical use as a terminal display device of a computer.

FIG. 3 shows an example of an active matrix substrate used in a conventional display device. The source bus wiring 5 is provided orthogonally to the gate bus wiring 24, and on the gate bus wiring 24 near the intersection of the gate bus wiring 24 and the source bus wiring 5,
TFT7 is provided. The source electrode 15 of the TFT 7 and the source bus line 5 are connected by a source branch line 8.
The drain electrode 16 of the TFT 7 is connected to the pixel electrode 6.
A gate insulating film 11 described later is interposed between the gate bus wiring 24 and the source bus wiring 5.

FIG. 4 is a sectional view taken along line IV-IV in FIG. 3 of a display device using the substrate shown in FIG. A base coat film 2 made of silicon nitride such as Ta ₂ O ₅ , Al ₂ O ₅ or Si ₃ N ₄ (hereinafter referred to as “SiN _X ”) is formed on the entire surface of the glass substrate 1, and the base coat film 2 is formed on the base coat film 2. A gate bus wiring 24 made of a metal such as Ta or W is patterned. The gate electrode 9 is formed as a part of the gate bus wiring 24,
Therefore, the gate electrode 9 is also made of a metal such as Ta or W. Metals such as Ta and W have high etchant resistance to etchants in, for example, the subsequent step of forming the TFT 7, so that a slight pin is formed on the gate insulating film 11 and the like formed on the gate bus wiring 24 and the gate electrode 9. Even if holes are present, these wirings 24 and electrodes 9 are not eroded.

A gate insulating film 11 made of SiN _X is formed on the entire surface of the substrate 1. The above-mentioned gate insulating film is formed on the gate electrode 9.
11 through amorphous silicon (hereinafter referred to as "a-S
The semiconductor layer protective film 13 made of SiN _x is formed on the intrinsic semiconductor layer 12. The semiconductor layer protective film 13 functions as an etching stopper in a later step of forming a source electrode and a drain electrode. On the intrinsic semiconductor layer 12 and the semiconductor layer protective film 13
Contact layers 14, 14 are provided on the top. Further, a source electrode 15 and a drain electrode 16 are formed on the contact layers 14 and 14, respectively, and a pixel electrode 6 made of ITO is connected to the drain electrode 16.

A large number of such pixel electrodes 6 are arranged in a matrix, and the TFTs 7 connected to each pixel electrode 6 are connected to the gate bus wiring 24.
The active matrix substrate is formed on the above. The source bus line 5 is the source electrode 15 of each TFT 7 arranged in a direction perpendicular to the direction of the gate bus line 24.
Are connected via the branch wiring 8.

Si is formed on the entire surface of the substrate 1 on which the TFT 7, the pixel electrode 6 and the like are formed.
A protective film 17 made of N _X is deposited, and an alignment film is formed on the protective film 17.
19 are formed. On the glass substrate 20 facing the glass substrate 1, a color filter 21, a counter electrode 22, and an alignment film.
23 are sequentially formed. A liquid crystal 18 is enclosed between the two substrates 1 and 20 to form an active matrix display device. In this display device, scanning signals are sequentially input to the gate bus lines 24, image signals are input to the corresponding source bus lines 5, and the pixel electrodes 6 are driven.

(Problems to be Solved by the Invention) In such an active matrix display device,
For high density display, a large number of pixel electrodes 6 and TFTs 7
It is necessary to place and. As the numbers of the pixel electrodes 6 and the TFTs 7 increase, the numbers of the gate bus lines 24 and the source bus lines 5 also increase. In a display device that displays a fine image, for example, 400 or more gate bus wires 24
And 600 or more source bus lines 5 are provided. In such a high-definition display device, the gate bus wiring 1
The writing time per book is several tens of microseconds. In a conventional display device using a metal such as Ta or W having a relatively large specific resistance for the gate bus wiring 24, it is not possible to apply a sufficient voltage to all the gate electrodes 9 within such a short time. That is, a signal delay occurs in a portion farther from the input section on the gate bus line 24 than in the vicinity of the input section. Due to this signal delay, a sufficient voltage is not applied to the pixel electrode 6 within the above writing time. Therefore, a display defect will occur in the picture element connected to the part of the same gate bus line 24 far from the input part.

In order to solve this problem, the gate bus wiring 24 and the gate electrode 9 are formed of a low resistance metal such as Al, Mo and Cu. However, when the gate bus wiring 24 is formed of such a metal material, these metal materials have low etchant resistance to an etchant used later, for example, in the step of forming the TFT 7 and the pixel electrode 6, so that the gate bus with few defects is formed. It is difficult to obtain the wiring 24. That is, if there are slight pinholes in the gate insulating film 11 and the resist formed thereon, the gate bus wiring 24 formed thereunder will be eroded by the etchant.

Further, it has been proposed that the gate bus wiring 24 has a two-layer structure, the lower layer is formed of the above-mentioned metal such as Al, Mo, and Cu, and the upper layer is formed of the metal such as Ta and W. Since metals such as Ta and W are relatively excellent in etchant resistance as described above,
Even after the subsequent etching process, a gate bus wiring with few defects can be obtained. However, in such a two-layer structure, due to the difference in internal stress generated in the upper layer and the lower layer, there is a new problem that film peeling is likely to occur in a later step.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide an active matrix display device having a scanning line having a low resistance and having sufficient etchant resistance even in a subsequent etching process. Is to provide.

(Means for Solving the Problems) In an active matrix display device of the present invention, a pair of substrates, at least one of which has a light-transmitting property, is enclosed between the substrates and the optical characteristics are modulated in response to an applied voltage. A display medium, a picture element electrode arranged in a matrix on an inner surface of one of the substrates, a switching element connected to the picture element electrode, and a scanning line connected to the switching element An active matrix display device,
The scanning line has a first wiring made of a low-resistance metal and a second wiring made of a metal having a high etchant resistance, and the second wiring has both front and back surfaces and both side surfaces of the first wiring. Are covered in a manner that surrounds, thereby achieving the above object.

(Operation) As a scan line having a two-layer structure in which the second wiring made of a metal having high etchant resistance covers the first wiring made of a low resistance metal having low etchant resistance, the second wiring is generally the first wiring. A structure having a structure that covers the surface (upper surface) and both side surfaces of the wiring 1 is used.

By the way, due to the difference in thermal stress generated in the heat treatment process in the manufacturing process, the internal stress generated in the upper second wiring and the lower first wiring is different. Therefore, due to the difference in the internal stress, in the scanning line of the covering structure, a gap is generated between the substrate surface and the lower surface of the portion of the second wiring which covers both side surfaces of the first wiring, The etchant penetrates through this gap, and the first etchant has a low etchant resistance.
Erodes the wiring of.

When the first wiring is eroded, its surface shape is deformed, so that a gap is formed in the joint surface with the second wiring. As a result, the above coating structure has a drawback that film peeling is likely to occur.

When film peeling occurs, a pixel defect occurs, and thus the yield of the active matrix display device decreases.

However, according to the present invention, the back surface of the first wiring, that is, the lower surface thereof is also covered with the second wiring made of a metal having a high etchant resistance. As a result, in the present invention, the first wiring is arranged at a position floating above the substrate surface. Therefore, due to the difference in internal stress, a gap is created between the substrate surface and the lower surface of the portion of the second wiring that covers both side surfaces of the first wiring, and the etching solution enters through this gap. However, the etching solution does not come into contact with the first wiring.

As a result, according to the present invention, the first wiring is not eroded by the etching solution, and therefore film peeling does not occur on the scanning line.

Note that the first wiring is formed of a metal such as Al, Mo, and Cu, and the second wiring is formed of a metal such as Ta and W. By forming with such a material, an active matrix display device having a scan line having low resistance and having sufficient etchant resistance in the subsequent etching step can be obtained.

(Examples) The present invention will be described below with reference to Examples. In Figure 1,
FIG. 3 is a plan view of an active matrix substrate used in the display device of the present invention. The source bus line 5 is provided orthogonally to the gate bus line 24, and a gate insulating film 11 described later is interposed at the intersection of the gate bus line 24 and the source bus line 5. A TFT 27 is provided on the gate bus line 24 near the intersection of the gate bus line 24 and the source bus line 5. The source electrode 15 of the TFT 27 and the source bus line 5 are connected by a source branch line 8. The drain electrode 16 of the TFT 27 is connected to the pixel electrode 6.

FIG. 2 is a sectional view taken along line II-II in FIG. 1 of a display device using the substrate of FIG. A base coat film 2 having a thickness of 3000 Å is formed on the entire surface of the glass substrate 1. Although the base coat film _{2 Ta 2 O 5, Al 2} O 5, SiN X ( e.g. Si ₃ N ₄₎ or the like is used, in the present embodiment using a Ta ₂ O _5. A gate bus line 24 for supplying a scanning signal is formed on the base coat film 2. The gate electrode 9 is formed as a part of the gate bus line 24.

In the present embodiment, the gate bus wiring 24 and the first wiring 25 are
It has a second wiring 26 covering the first wiring 25.
The second wiring 26 is formed by completely covering the first wiring 25. Similarly, the gate electrode 9 formed as a part of the gate bus wiring 24 has the first electrode 3 and the second electrode 4 covering the first electrode 3. The second electrode 4 is formed by completely covering the first electrode 3. The first wiring 25 and the first electrode 3 are made of Al-Si and have a thickness of 1500Å. The second wiring 26 and the second electrode 4 are
It is made of Ta and is formed to have a thickness of 1000 Å above and below the first wiring 25 and the first electrode 3, respectively.

An anodic oxide film 10 made of Ta ₂ O ₅ is formed on the second wiring 26 and the second electrode 4. The anodic oxide film 10 functions as a gate insulating film. A gate insulating film 11 made of SiN _X is entirely deposited on the anodic oxide film 10. The thickness of the gate insulating film 11 is preferably 1500 to 6000Å,
In this embodiment, it is set to 2000 to 3500Å.

An intrinsic semiconductor layer 12 made of a-Si is formed on the gate insulating film 11 above the gate electrode 9. Further, a semiconductor layer protective film 13 made of SiN _X is provided on the intrinsic semiconductor layer 12 in order to protect the upper surface of the intrinsic semiconductor layer 12.
The semiconductor layer protective film 13 functions as an etching stopper in a later step of forming a source electrode and a drain electrode.
On the intrinsic semiconductor layer 12 and the semiconductor layer protective film 13, an n-type a
Contact layers 14, 14 made of —Si are formed. The contact layers 14 and 14 are provided to make ohmic contact with the source electrode 15 and the drain electrode 16.

The source electrode 15 and the drain electrode 16 include Al, Mo, Ti,
Although a metal such as Ni is used, Ti is used in this embodiment and its thickness is 3000 Å. ITO on the drain electrode 16
Is connected to the picture element electrode 6. The source bus line 5 and the source branch line 8 are a source electrode 15 and a drain electrode.
Formed at the same time as 16. The source bus line 5 may have a two-layer structure like the gate bus line 24, but the number is one in this embodiment.

S is formed on the entire surface of the substrate 1 on which the TFT 27, the pixel electrodes 6 and the like are formed.
A protective film 17 made of iN _X is deposited. The suitable thickness of the protective film 17 is 2000 to 10,000 Å, but in this embodiment, it is about 5,000 Å. An alignment film 19 is formed on the protective film 17.

The gate insulating film 11 and the protective film 17 are formed of Si other than SiN _x described above.
O ₂ , Ta ₂ O ₅ , Al ₂ O ₅ and other oxides and nitrides can also be used. Further, the protective film 17 may not be formed on the entire surface as in the present embodiment, but may have a windowed structure removed at the central portion of the pixel electrode 6.

A color filter 21, a counter electrode 22, and an alignment film 23 are sequentially formed on a glass substrate 20 facing the above glass substrate 1. A liquid crystal 18 is enclosed between the two substrates 1 and 20 to form an active matrix display device.

In the display device of the present embodiment, the gate bus wiring 24 is Al-Si.
The resistance of the gate bus wiring 24 is reduced because it has the first wiring 25 consisting of. Therefore, a sufficient voltage can be applied to all the gate electrodes 9 on the gate bus wiring 24 within a writable time per one gate bus wiring 24, and the above-mentioned problem of signal delay is solved. It

Further, the first wiring 25 and the first electrode 3 are formed at the cores of the gate bus wiring 24 and the gate electrode 9, and the second wiring 26 and the second wiring 26 made of Ta metal are formed around them.
Electrode 4 is formed. Therefore, gate bus wiring
The first wiring 25 and the first electrode 3 are not exposed to the etchant by the etchant in the step of forming the TFT 27 after the formation of the gate electrode 24 and the gate electrode 9, for example.

Further, since Ta metal can be anodized, the anodized film 10 can be formed on the gate bus line 24 and the gate electrode 9. By forming the anodic oxide film 10, the first wiring 25 and the first electrode 3 can be more surely protected from an etchant in a later step.

Although the active matrix display device has been described in the above embodiments, the present invention is not limited to this. Further, although the case where the TFT is used as the switching element has been described in the present embodiment, the present invention is not limited to the above.
It can also be used for a display device using elements such as MIM elements, diodes, and varistor.

(Effect of the Invention) According to the above active matrix display device of the present invention, the scanning line has the first wiring made of a low resistance metal and the second wiring made of a metal having a high etchant resistance,
Since the second wiring covers both the front and back surfaces and both side surfaces of the first wiring in a surrounding form, both side surface portions of the first wiring of the second wiring are caused by the difference in internal stress. A gap is formed between the lower surface of the portion that covers the substrate and the substrate surface, and even if the etching liquid enters through the gap, the etching liquid does not come into contact with the first wiring.

For this reason, the first wiring is not eroded by the etching solution, so that the film is not peeled off from the scanning line.
As a result, the yield of the active matrix display device can be improved, and the cost of the display device can be reduced.

In addition, since a scan line having low resistance can be realized, it is possible to cope with an increase in size and definition of a display device.

[Brief description of drawings]

1 is a plan view of an active matrix substrate used in the display device of the present invention, and FIG. 2 is a sectional view taken along line II-II in FIG. 1 of the display device using the substrate of FIG. Third
FIG. 4 is a plan view of an active matrix substrate used in a conventional display device, and FIG. 4 is a sectional view taken along line IV-IV in FIG. 3 of the display device using the substrate of FIG. 1,20 ... Glass substrate, 2 ... Base coat film, 3 ... First electrode, 4 ... Second electrode, 5 ... Source bus wiring,
6 ... Pixel electrode, 8 ... Source branch wiring, 9 ... Gate electrode, 10 ... Anodized film, 11 ... Gate insulating film, 12 ... Intrinsic semiconductor layer, 13 ... Semiconductor layer protective film, 14 ...... Contact layer, 15 ...... Source electrode, 16 …… Drain electrode, 17 …… Protective film, 18 …… Liquid crystal, 19,23 …… Alignment film, 21 …… Color filter, 22 …… Counter electrode, 24 ・ ・ ・… Gate bus wiring, 25…
… First wiring, 26 …… Second wiring, 27 …… TFT.

Front page continued (72) Inventor Makoto Miyago, 22-22 Nagaikecho, Naganocho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) Toshihiko Hirobe 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation ( 72) Inventor Takayoshi Nagayasu 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture (56) References JP-A-2-184824 (JP, A) JP-A-60-43858 (JP, A) JP 61-193128 (JP, A) JP 61-173286 (JP, A)

Claims (1)

(57) [Claims] 1. A pair of substrates, at least one of which has translucency, a display medium which is enclosed between the substrates and whose optical characteristics are modulated in response to an applied voltage, and an inner surface of one of the substrates. An active matrix display device comprising: pixel electrodes arranged in a matrix in a matrix, switching elements connected to the pixel electrodes, and scan lines connected to the switching elements, wherein the scan lines are A first wiring made of a low resistance metal and a second wiring made of a metal having a high etchant resistance, wherein the second wiring surrounds both front and back surfaces and both side surfaces of the first wiring. Coating active matrix display.